Effect of high-temperature thermomechanical treatment on mechanical metallurgy characteristics of high-strength martensitic steels

Abstract

The high-temperature thermomechanical treatment of high-strength steels has proved to be superior to their conventional heat treatment in enhancing both their strength and their plastic properties, as well as in raising their fracture toughness K_IC and the threshold values of K_ISCC and K_ISH, established by testing in a 3·5% aqueous solution of NaCl and during electrolytic hydrogen charging of the specimens, respectively. Tests proved that high-temperature treatment increased the K_IC value for any selected ultimate tensile strength level by roughly 20 MPa/m^1/2, while the strength properties concurrently improved by some 12–15%. The mechanical metallurgy investigations were supplemented by a fractographic analysis. The favourable effect of high-temperature thermo mechanical treatment on the mechanical metallurgy properties is attributed to both the refinement of the martensitic structure and the limitation of the dynamic effects of the platelets in the course of the martensitic phase transformation.

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